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slip & noslip boundary conditions are wrong on dynamic mesh

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Old   February 17, 2016, 04:31
Default slip & noslip boundary conditions are wrong on dynamic mesh
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Olaf Schiemann
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Hello,
I have a small test case, which models the water flow inside a "bouncing cube", a rectangular mesh growing/shrinking periodically in the horizontal/vertical direction.
The motion of the walls is not transferred to the water, whatever boundary condition I use for the velocity (slip, no slip, fixedValue (0 0 0 )).

Do other boundary conditions or solvers exist which correctly interprete the slip or noslip conditions such that no relative (normal) velocity occurs between the moving wall and the fluid inside?

I am testing with rhoPimpleDyMFoam of OpenFOAM 2.4.0. You will definitely help me as well, if you know of a solution using another solver or OpenFOAM version.

Greetings
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Old   February 17, 2016, 08:59
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Jan
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Hi Olav,

try movingWallVelocity

Best regards,
Jan
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Old   February 17, 2016, 11:32
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Hi Jan,
thank you very much for your reply. Apparently, not the fluid velocity boundary condition was the problem, but the pointMotionUx boundary condition does not work quite as I need.

I am testing now with the incompressible/pimpleDyMFoam/movingCone tutorial. Changing the movingWall boundary in 0/U as follows works as expected:

Code:
    movingWall
    {
        type            movingWallVelocity;
        value           uniform (0 0 0);
        //type          fixedValue;
        //value         uniform (1 0 0);
    }
However, this simulation succeeds only if 0/pointMotionUx for movingWall is set to "uniformFixedValue=1". I had attempted first to use groovyBC and then my own, custom class (derived from fixedValuePointPatchField) instead of the uniformFixedValue. Below is an example, which uses groovyBC to express the same pointMotionUx==1, but this example fails, because the mesh is distorted after a few steps:
Code:
    movingWall
    {
        //type          uniformFixedValue;
        //uniformValue  constant 1;
        type            "groovyBC";
        value           uniform 1;
        valueExpression "toPoint(1)";
    }
Running this example translates the moving patch correctly, but the remaining mesh motion is not solved correctly (the internal mesh doesn't move).

Can you imagine a reason, why this fails, whereas the uniformFixedValue example succeeds?

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Old   February 18, 2016, 13:52
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Olaf Schiemann
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Quote:
Originally Posted by JNSN View Post
Hi Olav,

try movingWallVelocity

Best regards,
Jan
Although movingWallVelocity worked if pointMotionUx is "constant 1", there is a bug if pointMotionUx is variable in time.

I have attached a case file to reproduce the problem in this thread:

http://www.cfd-online.com/Forums/ope...implement.html

Greetings
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